In order to observe a fine region of an object, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and the like are used. Generally, in these devices, a housing in which the sample is disposed is evacuated so as to render the sample atmosphere into a vacuum state in which to image the sample. In this case, however, a biochemical sample, a liquid sample and the like may be damaged or turned into a different state by the vacuum. Meanwhile, there is much need for observing such samples using the electron microscope, and SEM devices and sample holder devices that enable observation of the sample as the object of observation in the atmospheric pressure have been developed in recent years.
These devices are in principle configured such that a separating film or a fine through hole through which an electron beam can be transmitted is disposed between an electron optical system and the sample to separate a vacuum state from the atmosphere state. The devices are similar in that the separating film is disposed between the sample and the electron optical system.
For example, Patent Literature 1 discloses an SEM in which the electron source side of an electron optical lens barrel is disposed downward and the objective lens side thereof is disposed upward, with the separating film through which the electron beam can be transmitted being disposed over an electron beam emission opening at the distal end of the electron optical lens barrel via O-rings. According to the invention described in this literature, a sample as the object of observation is directly placed on the separating film, and the sample is irradiated with a primary electron beam from a lower surface of the sample. Reflected electrons or secondary electrons are then detected to perform SEM observation. The sample is held in a space formed by the separating film and an annular member installed around the separating film, the space being filled with liquid such as water.